1. Field of the Invention
The present invention relates to an organic EL (electroluminescence) display.
2. Description of the Related Art
Recently, an organic EL display including an OLED (Organic Light Emitting Diode) has drawn attention. Thus, the organic EL display has been used as a display for a variety of products such as mobile phones or digital cameras.
The conventional organic EL display has a structure comprising a substrate, a plurality of organic EL elements arranged on the substrate, a barrier rib which is disposed between the adjacent organic EL elements and is disposed in order to surround each organic EL element, a protection layer which covers the organic EL elements, and a sealing member (a sealing substrate) for forming a sealed space between the substrate and the sealing member.
The organic EL element has a structure in which a lower layer electrode, an organic layer including an emission layer, and an upper layer electrode are sequentially laminated on the substrate. When power is supplied to the lower layer electrode and the upper layer electrode, hole and electron are injected towards the emission layer from the lower layer electrode side and the upper layer electrode side, respectively. The injected hole and electron are recombined in the emission layer to emit a specific light.
In general, the organic EL display is formed in the order of the substrate, the lower layer electrode, the barrier rib, the organic layer, the upper layer electrode, and the protection layer.
If the organic layer and/or the upper layer electrode are formed by using a deposition mask, the barrier rib serves to support the deposition mask. If the organic layer and the electrodes are formed through a deposition method without using the deposition mask, the barrier rib itself functions as the deposition mask. If the organic layer and the like are formed by using other methods excluding the deposition method (e.g. an inkjet method), the barrier rib can enhance electrical insulation between the adjacent pixels.
The barrier rib is formed of an organic material such as a novolak or acrylic-based resin, or a material including the organic material. Since the organic material can relatively easily absorb moisture, the barrier rib can easily absorb moisture from external air in the process of forming the organic layer, the upper layer electrode, and the protection layer. Thus, when the manufacturing process of the organic EL display is completed, there is a case in which much moisture is absorbed into the barrier rib. If the absorbed moisture is evaporated due to a change in an internal pressure of the display and the like, the evaporated moisture may enter between the barrier rib and the protection layer so as to reach the organic layer. In this case, the lifespan of the organic EL element may be shortened.
Meanwhile, Japanese Unexamined Patent Application Publication No. 2005-122924 and Japanese Unexamined Patent Application Publication No. 2003-257655 propose a technique in which a surface of a barrier rib is fluorinated by exposing the surface of the barrier rib formed of a resin to a fluoride gas.
However, basically, in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-122924 and Japanese Unexamined Patent Application Publication No. 2003-257655, the surface of the barrier rib formed of a resin is fluorinated. Therefore, if the moisture, which is absorbed by the barrier rib before a fluorination process is performed after the barrier rib is formed, is evaporated after the manufacturing process of the organic display is completed, there is still high possibility in that the evaporated moisture is absorbed between the fluorinated surface and an inner area of the surface so as to reach the organic layer. Further, impact of the fluorination process against the organic EL element has not been taken into account. Accordingly, there has been a demand for an organic EL display having a novel structure in which the lifespan of the organic EL element can be further improved.